温梯法蓝宝石（Al2O3）晶体的脱碳去色退火研究

温度梯度法（TGT）生长的Al2O3晶体因石墨发热体在高温时的挥发和原料中过渡性金属离子的存在，晶体在不同部位呈现不同颜色，一般上部为浅红色，尾部为浅黄绿色，将TGT法生长的Al2O3晶体（Ф110×80mm^3）依次经过高温氧化气氛、高温还原气氛脱碳、去色退火实验，即“两步法”退火实验，晶体变成无色、透明，经测试，Al2O3晶体的完整性、光学透过率和光学均匀性均有显著提高。

Diode-pumped Yb : YAG ceramic laser

Transparent polycrystalline Yb:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3, Y2O3, and Yb2O3 powders. The powders were mixed in ethanol and doped with 0.5 wt% tetraethoxysilane, dried, and pressed. Pressed samples were sintered at 1730 degrees C in vacuum. Transparent fully dense samples with grain sizes of several micrometers were obtained. The phase from 1500 degrees to 1700 degrees C was important for the grain growth, in which the grains grew quickly and a mass of pores were eliminated from the body of the sample. Annealing was an important step to remove the vacancies of oxygen and transform Yb2+ to Yb3+. The 1 at.% Yb:YAG ceramic sample was pumped by a diode laser to study the laser properties. The maximum output power of 1.02 W was obtained with a slope efficiency of 25% at 1030 nm. The size of the lasering sample was 4 mm x 4 mm x 3 mm.

Growth of high quality Cr, Yb codoped gadolinium gallium garnet (Gd3Ga5O12) crystal and its spectral properties

The Cr(0.1%),Yb(10%):GGG crystals have been grown by the Czochralski method. The chemical composition is: Yb0.33Gd2.47Cr0.005Ga5.2O12. There are no observed Yb3+ ions substituting Ga3+ ions, just like that of Yb:GGG crystals. The defects in Cr,Yb:GGG crystal were also investigated. The absorption and emission spectra of Cr,Yb:GGG crystal at room temperature have been measured. The 02 and H-2 annealing effect of Cr,Yb:GGG crystal have been compared. Cr3+ can greatly weak the visible luminescence of this crystal. The Cr-Yb-codoped crystals may be potential materials for compact, efficient, high stability LD pumped solid state lasers. (C) 2006 Elsevier B.V. All rights reserved.

Single crystal beta-Ga2O3: Cr grown by floating zone technique and its optical properties

beta-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in beta-Ga2O3 crystals Cr3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3+ intrinsic emission was enhanced and the green luminescence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from T-4(2) to (4)A(2). The studies manifest that the beta-Ga2O3 crystals have the potential application for tunable laser.

Spectroscopic properties of Yb:YAP crystal

The 10at% Yb-YAP crystal has been grown by the Czochralski method. The absorption and emission spectra and fluorescence lifetime of Yb:YAP crystal at room temperature were studied. There is a strong absorption band centered at 959 nm and the absorption cross-section of 1.51 × 10^-20 cm². The emission cross-section at 1040 nm is 0.6 × 10^-20 cm² and the fluorescence lifetime is about 1.2 ms. The effects of O₂-annealing on the spectral properties were studied. The spectroscopic properties strongly depended on the axis direction and b axis was the best direction for laser output. The spectrum parameters of Yb:YAP and Yb:YAG crystal were compared.}

提拉法Ti:LiAlO_2晶体的生长、缺陷及N_2退火研究

本文采用提拉法成功地生长了钛掺杂浓度为0.1%原子分数的LiAlO2单晶体,借助光学显微镜,结合化学腐蚀法,对Ti:LiAlO2晶体(100)面空气退火前后的缺陷特征进行了研究,用AFM观测了(100)面晶片在不同温度下流动N2气氛退火过的表面形貌。结果表明:Ti:LiAlO2晶体(100)面的位错腐蚀坑是底面为平行四边形的锥形坑,位错密度约为5.0×104cm-2,900℃空气退火后晶片表面的位错腐蚀坑变大;N2退火能显著影响晶片的表面形貌,当退火温度为900℃时,晶片的均方根粗糙度(RMS)达到最低值

温度梯度法生长Nd：YAG激光晶体的核心分布

用温度梯度法生长了直径为75mm大尺寸的Nd：YAG激光晶体，通过退火排除了生长过程中进入晶体的碳原子．用正交偏光显微镜观察了晶体的核心分布以及生长条纹．测试了室温下的吸收谱并利用吸收谱研究了Nd离子在YAG晶体中的分布．比较了温度梯度法与提拉法生长晶体的区别．

非晶硅薄膜制备及其晶化特性研究

用磁控溅射法在K9玻璃上沉积了非晶硅（a—Si）膜和a—Si／Al膜，并将其在流动的N2气氛下进行退火。对退火前后的样品进行Raman光谱、XRD和SEM表征和分析。Raman光谱表明随着退火温度的升高，a-Si膜的散射峰出现了明显的蓝移，但XRD结果表明薄膜仍为非晶态；而a—Si／Al膜在温度很低时就已经开始晶化。

Growth, etching morphology and spectra of LiAlO2 crystal

gamma-LiAlO2 single crystal was successfully grown by Czochralski method. The crystal quality was characterized by X-ray rocking curve and chemical etching. The effects of air-annealing and vapor transport equilibration (VTE) on the crystal quality, etch pits and absorption spectra of LiAlO2 were also investigated in detail. The results show that the as-grown crystal has very high quality with the full width at half maximum (FWHM) of 17.7-22.6 arcsec. Dislocation density in the middle part of the crystal is as low as about 3.0 x 10(3) cm(-2). The VTE-treated slice has larger FWHM value, etch pits density and absorption coefficient as compared with those of untreated and air-annealed slices, which indicates that the crystal quality became inferior after VTE treatment. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Edge-defined, film-fed growth (EFG) technique for the preparation of alpha-Al2O3 : C crystal with highly sensitive thermoluminescence response

In this work, alpha-Al2O3:C, a highly sensitive thermoluminescence dosimetry crystal, was grown by the EFG method in which a graphite heating unit and shield acted as the carbon source during the growth process. The optical, luminescent properties and dosimetric characteristics of the crystal were investigated. The as-grown crystal shows a single glow peak at 536 K, which is associated with Cr3+ ions. After annealing in H-2 at 1673 K for 80 h, the crystal shows a single glow peak at 460 K and a blue emission band at 415 nm. The thermoluminescent response of the annealed crystal shows linear-sublinear-saturation characteristics in the dose range from 5 x 10(-6) to 100 Gy.

Effect of microstructure of TiO2 thin films on optical band gap energy

TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4 eV to 3.21 eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.

Investigation on microstructure and optical properties of titanium dioxide coatings annealed at various temperature

TiO2 coatings were prepared on fused silica with conventional electron beam evaporation deposition. After TiO2 thin films were annealed at different temperatures for 4 h, several properties were investigated by X-ray diffraction (XRD), spectrometer.. photoelectron spectroscopy (XPS) and AFM. It was found that with the annealing temperature increasing, the transmittance of TiO2 coatings decreased, and the cutoff wavelength shifted to long wavelength in near ultraviolet band. Especially, when coatings were annealed at high temperature, the optical loss is very serious, which can be attributed to the scattering and the absorption of TiO2 coatings. XRD patterns revealed that only anatase phase was observed in TiO2 coatings regardless of the different annealing temperatures. XPS results indicated that the fine chemical shift of TiO2 2p(1/2) should be attributed to existence of oxygen vacancies around Ti+4 ion. The investigation on surface morphology by AFM showed that the RMS of titania thin films gradually increases from less than 0.40 nm to 5.03 nm and it should be ascribed to the growth of titanium dioxide grain size with the increase of annealing temperature. (C) 2005 Elsevier B.V. All rights reserved.

Optical, structural and laser-induced damage threshold properties of HfO2 thin films prepared by electron beam evaporation

We prepare HfO2 thin films by electron beam evaporation technology. The samples are annealed in air after deposition. With increasing annealing temperature, it is found that the absorption of the samples decreases firstly and then increases. Also, the laser-induced damage threshold (LIDT) increases firstly and then decreases. When annealing temperature is 473K, the sample has the highest LIDT of 2.17J/cm(2), and the lowest absorption of 18 ppm. By investigating the optical and structural characteristics and their relations to LIDT, it is shown that the principal factor dominating the LIDT is absorption.

Study of Al2O3/MgF2 HR coatings at 355 nm

With the present work we tried to study the effective methods to improve the laser-induced damage threshold (LIDT) and reflectance of HR coatings at 355 nm. The work presented in this paper wits part of an ongoing study about vacuum annealing. It was dedicated to study the effects Of Vacuum annealing with different temperature gradients on the structure, optical properties and laser-induced damage threshold (LIDT) of 355nm Al2O3/MgF2HR coatings. A number of samples were prepared by electron beam evaporation using the same deposition process with an optimal deposition temperature of 280 degrees C. After deposition, samples were annealed in the coating chamber for 3 h with different temperature gradients. Morphologies of the samples were observed by Leica-DMRXE. Microscope, Structure of the samples had been characterized by X-ray diffraction (XRD). Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer, The LIDT of the samples was measured by a 355 nm Nd:YAG laser with a pulse width of 8 ns. It was found that the temperature gradient of vacuum annealing had significant effects on the morphology, structure, absorption, and LIDT of the samples, (c) 2005 Elsevier Ltd. All rights reserved.

Structure and UV emission of nanocrystal ZnO films by thermal oxidation of ZnS films

ZnO films prepared by the thermal oxidation of the ZnS films through thermal evaporation are reported. The as-deposited ZnS films have transformed to ZnO films completely at 400 degrees C. The 400-700 degrees C annealed films with a preferential c-axis (002) orientation have a hexagonal wurtzite structure. The band gap of ZnO films shifts towards longer wavelength with the increase of the annealing temperature. The relationship between the band gap energy of ZnO films and the grain size is discussed. The shift of the band gap energy can be ascribed to the quantum confinement effect in nanocrystal ZnO films. The photoluminescence spectra of ZnO films show a dominant ultraviolet emission and no deep level or trap state defect emission in the green region. It confirms the absence of interstitial zinc or oxygen vacancies in ZnO films. These results indicate that ZnO film prepared by this simple thermal oxidation method is a promising candidate for optoelectronic devices and UV laser. (c) 2005 Elsevier BN. All rights reserved.